In a bowl mix together the yeast, water and sugar.Leave in a warm place for 15 minutes, or until frothy.Mix together the flour, oil, salt and the frothy yeast mixture until the dough is a smooth round ball. (This is a workout!)Place the ball in a large well oiled bowl and cover with glad wrap.Leave in a warm place for an hour, until it has doubled in size.Turn out onto a well floured surface and knead for 2-3 minutes.Flatten out into a larger oiled roasting dish, to about 2cm thick.Cover with glad wrap and leave to rise for 30 minutes.Preheat the oven at 200C.Using your fingers and/or knuckles make indentations over the bread and brush with olive oil.Sprinkle with fresh rosemary and sea salt.Bake for about 45 minutes or until golden.